Refactor query parameter constants and update tests (#52)

Refactor query parameter constants in Getty Images API integration

- Replaced `Constants.EndDateKey` with `Constants.DateToKey` in `AddQueryParameter`.
- Replaced `Constants.StartDateKey` with `Constants.DateFromKey` in `AddQueryParameter`.
- Removed obsolete constants (`Constants.EndDateKey` and `Constants.StartDateKey`).
- Updated and adapted tests to reflect the changes in constants.

Bump System.Text.Json from 8.0.4 to 8.0.5 in /GettyImages.Api (#51)

Bumps [System.Text.Json](https://github.com/dotnet/runtime) from 8.0.4 to 8.0.5.
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](dotnet/runtime@v8.0.4...v8.0.5)

---
updated-dependencies:
- dependency-name: System.Text.Json
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Merge pull request #49 from gettyimages/dependabot/nuget/GettyImages.…

…Api/System.Text.Json-8.0.4

Bump System.Text.Json from 8.0.3 to 8.0.4 in /GettyImages.Api

Fix publish tests (#48)

AiGenerator functionality (#47)

Add functions for currently-available AI-generated content endpoints:

- Generate images from a prompt
- Get variations on a generated image
- Download generated images

Package, actions upgrades (#46)

* Package upgrades
* .NET 8 SDK and for Unit Test project
* Update all GitHub actions

Fix token expiration logic (#45)

Merge pull request #44 from gettyimages/new_auth_endpoints

Use new auth endpoints

Merge pull request #43 from gettyimages/add_getapiclientwithapikey_cr…

…edential_option

Add GetApiClientWithApiKey credential method

Merge pull request #42 from vigitri/fix_handle_unknown_orientation

Add Unknown value to orientation enum for images response